The tremendous increase in utilization of computers and mobile terminals in the representation of documents has established a development of applications for viewing the documents in different data formats. Most known examples are MICROSOFT™ OFFICE™ and ADOBE™ ACROBAT™ applications. Nowadays a typical situation is that a user is reviewing a document with his or her terminal device wherein the document is downloaded from a server residing in Internet. In such use case there needs to be a viewer application for the document in the terminal device which is capable of interpreting the document data in order to displaying the document content. One challenge in the above described situation is that the terminal devices as of today have limited computing power and it may happen that the terminal device cannot execute the viewer application with the received document. Alternatively, it may be that it is not allowed to deliver the document to the terminal device e.g. due to security reasons. These challenges are at least partly solved by arranging application software into a server end, which is configured to create images from the document contents. The images are then delivered to the terminal devices for displaying. This kind of approach brings some other challenges typically relating to the small display size and accuracy of the images when displayed and zoomed.
Another aspect is that along the development of web technologies the HTML (HyperText Markup Language) has brought some flexibility for displaying textual content in terminal device. The CSS (Cascading Style Sheets) technology, which belongs to the HTML area, has enabled a downloading of font information to the viewer application, such as Internet browser, residing in the terminal device from a server. The downloaded font information, and thus the font, is used in visualization of text located at a certain HTML page with the terminal device. This technique is called as web fonts. However, being quite a new technology the web fonts is continuously evolving. For example, Internet browsers support different techniques within the web font area and it forces the content providers to support different web font formats in order to support different browsers installed in terminal devices.
However, there are still challenges within the web font area, especially in processes and technologies how web fonts are created based on the existing font data. At least part of these problems originates from different document formats and their capabilities to carry font information as embedded or in a separate file related to the document. For example, if the font information is embedded in a PDF (Portable Document File) document, how the font information shall be extracted and processed for web font use. Moreover, many times the font information related to a document lacks of essential information and it has to be completed in order to be able to utilize such font information when creating web fonts. Also, the font information related to the source file shall be validated in order to confirm that it is complete, structurally and semantically valid, and can thus function as it should. Without such a validation there exists a risk of creating inoperative, faulty and/or even harmful web font information for the viewer applications residing the terminal device. At least some of the mentioned problems within the font area originate from a process and a tool by means of which the documents are produced as well as from tools developed to display the document contents. Some of the tools and processes therein do not follow the specifications set for a certain document type or font file. Alternatively, those specifications have been too loosely defined, and do not take account web font technology specific details.
Also, as the web fonts are transferred from a server to the terminal device it is important to confirm that the web font information, and thus the content, is downloadable in a rapid way. One additional aspect is that charging in one type of mobile communication subscriptions is based on the amount of transferred data which results that it is advantageous to minimize the amount of information as regards web font information.